Weight, strictly speaking, is the force required to support your body in a gravitational field. It's tightly related to your mass, but your mass is something that never changes, regardless of gravity or acceleration.

On Earth, if you have a weight of 50kg, you'll also have a mass of 50kg, because the definition of mass was made upon the Earth's surface, but if you went up to the Moon you'd only weigh 1/6 of that because, although your mass would remain 50kg, the Moon's gravity would only pull you down 1/6 as strongly as on Earth.

Now let's say that before you went to the Moon you took part in a little experiment; you sat on a wheelchair (with very low friction bearings) that was pushed up against a spring attached to a wall, so that when the spring was released it pushed you away from the wall, and you measured how fast you were going after the spring was fully extended. If you then try the same experiment on the Moon you'll find that although you now only weigh 8.33 kg, instead of 50kg, you will still only reach the same speed as on Earth.

With the spring experiment, what we've done is to effectively set up an artificial gravity at right angles to real gravity. When we then move to the Moon we can see by your reduced weight how gravity has changed and how, because you reach the same speed with the spring, that the spring hasn't changed on the Moon.

What you say at the end is correct then; the regular scale just registers the pull of gravity upon your mass.

I was just trying to address weight and mass - once that was clear I thought we could move on to forces and Newtons. I didn't want to complicate it too much to start with, but perhaps I should have left the answer to better teachers.

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